1. Field of the Invention
The present invention is related to a structure of grinding medium controllable in shape and specific gravity, and especially to a structure of grinding medium comprised of a housing, a cover, a spring and a core. The structure is used to precisely control specific gravity of grinding medium, and capable of assembling/changing springs of different sectional shapes and degrees of stretching and retracting. Thereby, the contour of blades on the external surface of the structure of grinding medium can be under control, thus chance and efficiency of grinding of a work piece to be ground can be increased.
2. Description of the Prior Art
The grinding technique using a vibration motor or supersonic-wave vibrating objects to generate multiple dimensional vibration is well known, it includes the steps of selecting desired grinding liquid and grinding granules of suitable diameters, hardness and shapes in accordance with physical characteristics of the workpieces to be ground. The grinding granules used to be made of plastic, stones or ceramic of various hardness and mass. The conventional grinding granules are made with shapes in favor of grinding, to facilitate the mixed grinding granules and grinding liquid to be subjected to desired vibration frequency as well as grinding process of multiple dimensional vibration in a vibration tank.
It is also known that the grinding technique using a vibration motor as a vibrating source to generate multiple dimensional vibration uses a large mount of grinding granules to envelop the workpieces to be ground in a vibration tank. Wherein, the vibration motor makes the vibration tank vibrate to synchronically disturb the grinding granules in the vibration tank to collide the workpieces to be ground and gives grinding and finishing function on the workpieces. Conventionally used grinding granules have larger mass in order to get larger vibrational inertia of the grinding granules for obtaining better grinding and finishing function. However, the grinding granules of larger mass make trouble of accumulation of themselves in the bottom layer of the vibration tank to get the result that the grinding granules are distributed denser in the bottom layer, and looser in the surficial layer. Therefore, chance of collision between the grinding granules and the workpieces to be ground in the surficial layer is lowered. And when in multiple dimensional vibration, the workpieces to be ground can not be uniformly ground, longer grinding time is required to get higher chance of grinding between the grinding granules and the workpieces to be ground. This is why efficiency of grinding thereof is inferior.
Further, the vibration technique using supersonic-wave objects as the source of multiple dimensional vibration generates supersonic waves to obtain consonant vibration of grinding liquid and a vibration tank and to make the grinding liquid form oscillating water flow of high frequency. The water flow makes the grinding granules vibrate to synchronically oscillate to collide the workpieces to be ground and gives grinding and finishing function on the workpieces. However, specific gravity of conventional grinding granules is determined by the mass and volume of their own and hard to control to approach that of the grinding liquid. This makes the grinding granules concentrate at the surface of the grinding liquid or the bottom of a vibration tank. The suitable pending position of the grinding granules is hard to control; therefore, chance of collision between the grinding granules and the workpieces to be ground is lowered. Hence, longer grinding time or higher supersonic wave frequency is required to increase chance of collision; the fact that grinding efficiency is inferior is evident.
And more, shapes of conventional grinding granules are certain and simple, they are lack of variety in favor of grinding. Therefore, when every grinding granule makes multiple dimensional vibration on the workplaces to be ground, grinding operation will be hindered by limited cutting points. This is the defect of the conventional grinding granules.
And the above stated problems to be solved are the motive of the present invention.